In long term evolution (LTE) systems, two parameters are defined for all non-guaranteed bit rate (non-GBR) bearers, one is Access Point Name-Aggregate Maximum Bit Rate (APN-AMBR) and the other is UE-Aggregate Maximum Bit Rate (UE-AMBR). The APN-AMBR is stored in a Home Subscriber Server (HSS) as subscription information, which limits the aggregate bit rate that can be expected to be provided across all Non-GBR bearers related to the same access point name (APN). Traffic exceeds the limit will be discarded. Any non-GBR hearer can utilize all APN-AMBR resources, if the other non-GBR bearers do not carry any traffic. Both Packet Data Network Gateway (PDN GW) and UE need to save the value of the APN-AMBR and perform rate shaping for hearers corresponding to both uplink (UL) and downlink (DL) traffic.
HSS also stores a subscribed UE-AMBR. The UE-AMBR limits AMBR provided by the network for all non-GBR bearers of a UE. Traffic exceeds the limit will be discarded. Any non-GBR bearer can utilize all UE-AMBR resources, if the other non-GBR bearers do not carry any traffic. Rate control nodes, the DL and UL bearers of which are based on the UE-AMBR are located in a base station (eNB), so the eNB has to store the value of UE-AMBR. The value used by the eNB for practical scheduling is dynamically provided by the MME. The MME compares the sum of APN-AMBR of all activated APNs with the subscribed UE-AMBR, and provides the eNB with the smaller one of the two values as to-be-used UE-AMBR.
When a UE is handed over between different eNBs, the MME may not change (X2 handover), or may change (S1 handover). In a handover prepare procedure, the UE-AMBR is sent to a target eNB by a source eNB during an X2 handover or by a target MME during an S1 handover. The value of the UE-AMBR sent in the handover prepare procedure is generated based on conditions of bearer connections established between the UE and the source eNB. During the handover, however, the target eNB may only accept part of the bearers and reserve resources for these bearers, and part of the bearers the resources of which are not reserved will not be established at the target side during the handover, thus the bearer connections between the UE and the target side may suffer a change. If the target eNB still performs scheduling by using the same UE-AMBR with the source side, the scheduling may be inaccurate and may adversely impact transmission performances of the network.